type Vertex2 = [number, number];
type Vector2 = [number, number];

let Direction2D = (v0: Vertex2, v1: Vertex2):Vector2 => {
    let dX = v1[0] - v0[0], dY = v1[1] - v0[1];
    return [dX, dY]
};

export {Direction2D, Vertex2, Vector2};